Use composite nodes in blender video sequence editor
While you can't use composite nodes directly in VSE strips, you can setup the compositor with an image sequence or video file input without adding any elements from the 3d scene.



Then in the VSE you can add a scene strip which gets the composited render results, so you can mix in audio and use any VSE specific features. You can also setup multiple scenes with different composite nodes and join them all in the VSE.